Electromagnetic actuator having a pair of electromagnets with an armature movable between them



June 24, 1969 R. R. SEIDLITZ 3,452,253

ELECTROMAGNETIC ACTUATOR HAVING A PAIR OF ELECTROMAGNETS. WITH AN ARMATURE MOVABLE BETWEEN THEM Filed March 14, 1967 INVENTOR RAYMOND R. SEIDLITZ AT TOR NEY United States Patent ELECTROMAGNETIC ACTUATOR HAVING A PAIR OF ELECTROMAGNETS WITH AN ARMATURE MOVABLE BETWEEN THEM Raymond R. Seidlitz, Rolling Meadows, 11]., assignor to Teletype Corporation, Skokie, 111., a corporation of Delaware Filed Mar. 14, 1967, Ser. No. 623,060 Int. Cl. H01h 47/04, 9/54; H01f 7/18 US. Cl. 317-155 7 Claims ABSTRACT OF THE DISCLOSURE Background of the invention In magnetic devices for transferring an armature back and forth between two electromagnets at high speeds, a high voltage source usually is needed to overcome the inductance of either electromagnet and rapidly to increase the current flowing through the winding of that electromagnet. In addition, a high current must be passed through the winding of the electromagnet in order to develop the strong magnetic field required to transrfer the armature rapidly from one electromagnet to the other. After the armature has completed its motion, however, it can be held in position with a very small current passing through the winding of the electromagnet since the magnetic field required to hold the armature in position is considerably less than that required to move the armature. The significant amount of power which must be available to an electromagnet to overcome the inductance of the magnet windings and to move the armature through a large air gap rnust be dissipated during the periods in which the eletcromagnet is only holding the armature. This results in undue circuit complexities and large and expensive power supplies.

Summary of the invention Therefore, it is an object of the present invention to supply a holding current to an electromagnet with a minimum of power dissipation.

It is another object of the present invention rapidly to generate a magnetic field for transferring an armature from One electromagnet to another.

A further object of the present invention in an electromagnetic switch having a pair of electromagnets with an armature movable between them, is to reduce the magnetic field of the magnet holding the armature and simultaneously to increase the magnetic field of the other magnet to attract the armature.

3,452,253 Patented June 24, 1969 In accordance with the preferred embodiment of the present invention, a pair of two-winding electromagnets are arranged at opposite extremes of the physical travel of an armature which is movable between them. One winding on each of the electromagnets functions as an energizing winding, and the other windings are used as holding windings, with the holding windings being connected in series. In the absence of any current in either of the energizing windings, the armature is held attracted to one of the electromagnets by the flux created by the current flowing through the holding winding of that electromagnet. When it is desired to attract the armature to the other electromagnet, current is applied through the energizing winding of that other electromagnet to increase the energization thereof. At the same time, the current flowing through the holding winding of the electromagnet being energized is reduced by transformer action. Since the holding windings are connected in series, the current flowing through the holding winding of the electromagnet originally attracting the armature is reduced to release the armature for travel to the other electromagnet. When attraction of the armature has been completed, current flow through the energizing winding is terminated. The sudden reduction of current in the energizing winding generates a voltage in the holding windings which aids the voltage generated by the source of current for the holding windings, causing holding current to be re-established.

Brief description of the drawing Other objects and features of the present invention will be apparent to those skilled in the art upon consideration of the following detailed description taken in conjunction with the accompanying drawing which shows a schematic diagram of the electrical energization circuit for a pair of two-winding electromagnets according to the preferred embodiment of the invention.

Detailed description Referring now to the drawing, an armature 10 of ferromagnetic material is pivotally mounted on a fixed support 11 and is free to move between two extreme positions. One of a pair of two-winding electromagnets 15 and 16 is placed at each extreme position of the movement of the armature 10, and the electromagnets 15 and 16 are arranged so that energization of the electromagnet 15 causes the armature 10 to move leftwardly, and energization of the magnet 16 causes the armature 10 to move rightwardly about pivot 11. A first winding 17 of the magnet 16 is connected in series with a corresponding winding 18 of the magnet 15 which in turn is connected to the positive terminal of a battery 20 to complete an electrical circuit from the battery 20 through the winding 18 and the winding 17 to ground. The current flowing through the windings 17 and 18 generates a magnetomotive force at each magnet 16, 15 causing sufficient magnetic flux to flow in the armature to hold the armature 10 against either magnet, once the armature 10 is placed in that position. It should be noted that this holding current may be much less than the energizing current required to attract the armature 10.

In the drawing the armature is shown positioned adjacent the magnet 15. To trans-fer the armature 10 from the magnet to the magnet 16, an additional magnetomotive force must be developed at the magnet 16 to generate sufficient magnetic flux between the armature 10 and the magnet 16 to attract the armature 10 away [from the magnet 15. At the same time, the holding current flowing through the coil 18 of the magnet 15 should be reduced in order to cause the magnet 15 more readily to release the armature.

A battery 21, having the same potential as or a different potential from the battery 20, is connected through a parallel network of a resistor and a capacitor 26 to an energizing winding 30 of the magnet 16. The winding 30, which has approximately five to twenty percent as many turns as winding 17, is connected through a normally open contact 31 to ground. When the contact 31 is closed, a current path is completed from ground through the battery 21, either the resistor 25 or the capacitor 26, the coil 30 and the contact 31 back to ground. The current that flows through the winding 30 when the contact 31 closes causes an increase in the flux flowing through both the magnet 16 and the armature 10.

The current flowing through the winding 30 initially increases very rapidly, and the magnetic coupling between the windings 30 and 17 permits the current in the winding 30 to supplant the current in the winding 17 in the generation of the magnetomotive force that causes flux to flow through the magnet 16. As the current flowing through the winding 30 increases, the flux flowing through the magnet 16 increases causing a voltage to be developed across the winding 17 in a polarity to oppose the flow of current through winding 17 from the battery 20. This impedes the holding current flowing through winding 18 as well as winding 17 since the windings are connected in series, and the holding current flowing through the two magnets is reduced to almost zero. Since the holding magnetism developed at the magnet 15 is dependent solely upon the current flowing through the winding 18, the magnet 15 releases the armature 10 when this holding current is reduced by the increased current flowing through the winding 30 of the magnet 16. At the same time, the increased flux at the magnet 16 attracts the armature 10 with increasing force and the armature moves rightwardly away from the magnet 15 and into engagement with the magnet 16. The switch 31 then can be opened, and the resulting sudden reduction of current in the winding 30 generates a voltage in the winding 17 which tends to aid the voltage generated by the battery 20. This causes the holding current to be restored in the windings 17 and 18, holding the armature 10 in engagement with the magnet 16.

In order to transfer the armature 10 from the magnet 16 back to its original position in engagement with the magnet 15, a contact 35 which is connected to a winding 36 of the magnet 15 is closed. This completes a current path from ground, through the battery 21 and a parallelconnected RC circuit comprising a resistor 37 and a capacitor 38, the winding 36, and the contact 35 back to ground. The current flowing through the winding 36 tends to increase the flux flowing through the magnet 15 and the armature 10 and reduces the flow of holding current in the windings 17 and 18, thereby releasing the armature from the magnet 16. The increased flux in the magnet 15 attracts the armature 10 from the magnet 16 to the position shown in the accompanying drawing; wherein the armature 10 is in engagement with the magnet 15. The subsequent opening of the contact 35 causes the holding current to be re-established in the windings 17 and 18 in the same manner as described previously.

It can be seen that the increase in flux brought about by the energization of either of the windings 30 and 36 decreases the energization of the windings 17 and 18 through transformer action and thereby decreases the .modifications which do not constitute energization of the electromagnet which is not receiving increased energization from the battery 21. The decrease in energization of the unselected magnet causes that magnet to release the armature 10, permitting the armature 10 to move to the magnet experiencing increased energization.

Contacts 31 and 35 have been shown as normally-. open switches; however, they readily can be replaced by electronic switching circuits which perform a similar function. Since other modifications of the electromagnetic switch varied to fit particular operating conditions will be apparent to those skilled in the art, the invention is not to be considered limited to the embodiment chosen for purposes of disclosure, and covers all changes and departures from the true scope of the invention. I I

I claim: I

1. A magnetic actuating device for moving an armature between two terminal positions, comprising:

a pair of electromagnets, each arranged to attract the armature to a terminal position;

means for supplying energization to the electromagnets for holding said armature in a terminal position; means for increasing the energization of one of the electromagnets for attracting the armature thereto;

and V means responsive to the increased energization of said one electromagnet for decreasing the energization of the other electromagnet to release the armature therefrom.

2. A device according to claim 1 wherein each electromagnet includes at least a first electrical winding and wherein the supplying means comprises means for passing an equal amount of current through the first windings of the two magnets. I

3. A device according to claim 2 wherein each electromagnet includes a second electrical winding and wherein the increasing means comprises means for passing current through the second winding of said one electromagnet. I

4. A device according to claim 3 wherein both windings of each electromagnet surround a common magnetic circuit, whereby an increase in the current flowing in the second winding of said one electromagnet induces a voltage across the first winding of said one electromagnet in a polarity to generate a current which opposes the current flowing in the first windings of both electromagnets y from the supplying means. I 1

5. An electromagnetic actuator including: an armature movable between two diametrically op- I posed terminal positions; a first two-winding electromagnet having at least one pole face arranged magnetically to cooperate with a surface of the armature for attracting the armature to one of said terminal positions; I I a second two-winding electromagnet having at least one pole face arranged magnetically to cooperate with a surface of the armature for attracting the armature to the other of said terminal positions; means for connecting the first windings of the first and second magnets in series; means for passing a current through the series-connected first windings to energize the magnets to hold the armature in a terminal position adjacent one electro- .magnet; I

means for passing current through the second winding of the other electromagnet to increase the energization of said other electromagnet; and means responsive to the increased energizatio'n'of said other electromagnet for decreasing the energization of said one electromagnet thereby releasing" the armature from said one electromagnet for movement to said other electromagnet.

6. An actuator according to claim 5 wherein the means for decreasing the energization of said one electromagnet comprises the first and second windings of each electromagnet linked by a common magnetic circuit so that a change in the current flowing in either of the second windings induces a voltage across the first winding of the electromagnet linked to the second winding, said voltage being of a polarity to generate a current which opposes the current from the current passing means in the first windings When the current in the second winding is increased and which generates a current which aids the current from the current passing means in the first windings when the current in the second winding is decreased.

7. An actuator according to claim 6 wherein the means for passing current through the second winding of the other electromagnet is operative only momentarily.

References Cited UNITED STATES PATENTS Catlin 178'/1 Craft 246231 Senn et a1. 317155.5 Hardison 317-151 Albosta 335-183 XR McCoy 317-1555 XR Pearse 317-1555 XR U.S. Cl. X.R. 

